Toxicological Studies Of Trichlorfon On Marine Microalgae

The effects of trichlorfon, a common organophosphorus insecticide, on thegrowth of three important microalgae species, Skeletonema costatum, Chattonellamarina and Scrippsiella trochoidea, were studied. Meanwhile the physiologicalresponses of S. costatum to trichlorfon, such as superoxide dismutase (SOD),malondialdehyde (MDA), catalase (CAT), soluble protein and soluble sugar contents,were measured as well to reveal the toxicological mechenisms of trichlorfontrichlorfon to marine microalgae. The purpose of this study is to assess the potentialeffects of trichlorfon on marine primary productivity and marine ecosystem.The72h EC50values of trichlorfon to Skeletonema costatum, Chattonella marinaand Scrippsiella trochoidea was84.8mg/L,32.1mg/Land22.1mg/L respectively.The effects of trichlorfon on the growth of algal cells showed significant dose-effectrelationships at72h acute exposure for all of the three species, and the inhibitoryeffects increased as the increase of concentration. While the growth of algal cells wassignificantly stimulated at the late period of the28-31d sub-chronic exposure due tothe decrease concentration of trichlorfon, phosphuros release from the degradation oftrichlorfon, and the compensatory growth of algal cells. The results suggested that thepollution of organophosphorus insecticides would stimulate the growth ofphytoplankton. And meanwhile the decrease of grazing pressure from zooplanktondue to their high sensitivity to organophosphorus insecticides would promote thegrowth of phytoplankton, and thus increase the risk of algal blooms.All phycilogical parameters responded to trichlorfon significantly and quickly.All parameters varied significantly within24h exposure, however tended to the basiclevel after24h or48h exposure. Superoxide dismutase (SOD) activities and solubleprotein contents were inhibted at high concentrations of trichlorfon, and stimulated atlow concentrations. Trichlorfon at concentrations≤25mg/L enhanced soluble proteinsignificantly. The maximum content occurred at12h exposure at the concentration of1mg/L, which was2.1times of that in the contral group. While the response of SODwas more sensitive, and SOD activities were significantly stimulated at concentrations≤5mg/L. The maximum SOD activity was two times of that in control group, occurring at12h exposure at the concentration of5mg/L. The contents of MDA andsoluble sugar increased as the increase of concentration, and showed a clear dose-response relationship. The results suggested that the inhibition of SOD activity andlipid peroxidation might play an important role in the mechanism of toxicity oftrichlorfon to marine microalgae.